Question { Prozone, 22162 }

If excitation will increase, then what will be the effect
on power factor? Will it decrease or increase?

Answer

it will depend upon a machine.

alternator:
excitation current will increase means power factor will decrease bcoz E is increased & resultant E induced and load current phase angle is reduced so power factor reduced

synchronous motor
on over excitation it will increase a power factor.

Question { 8250 }

What are the methods used to improve powerfactor ?

Answer

synchronous motor is used to improve power factor method and also capacitor.

when:

a synchronous motor working on no load in over excitation means it is possible.

how:

when current is lead the voltage power factor will improved.

Question { BARC, 39137 }

what is the difference between synchronization and paralleling?

Answer

parallel

any two or more alternator connected to grid and share a common load its called a parallel operation.

synchronizing

how to connect to grid (depend a voltage,frequency,phase sequence)a alternator is called a synchronizing operation.

Question { 7712 }

whta is difference between contactor and breaker.

Answer

contactor:
A contactor is an electrically controlled switch used for switching a power circuit, similar to a relay except with higher current ratings.

circuit breaker:
A circuit breaker is an automatically operated electrical switch designed to protect an
electrical circuit from damage caused by overload or short circuit. Its basic function
is to detect a fault condition and, by interrupting continuity, to immediately discontinue
electrical flow......

so finally,contactor used for switching.......and circuit breaker is used for to protect a circuit.so that one is interrupt device.....

Question { 6443 }

why we choose 50 or 60 hertz not other value for the power
system?

Answer

because the internal current goes up and this might cause faster deteriation of the insulation on the wiring, which causes shortcircuit and this may lead to fire, which can burn down your house!

What happens:
In transformers (like input transformer of the equipment) the current goes up.

In motors (like cooling ventilator or compressor) also the current goes up, the turns of the motor depends on the frequency, which means the turns are 17% higher if you go from 50 Hertz to 60 Hertz and 17% lower if you go from 60 Hertz to 50 Hertz, plus in this case the internal cooling is lower!

Question { Juniper Networks, 5490 }

What is the difference between Ac curent & DC current

Answer

A.C current having a sinusoidal wave form...D.C current having a straight live wave form.....in A.C power having a power factor....in D.C circuit not having a power factor...

Question { 3202 }

What is flow
meter?

Answer

A flowmeter is an instrument used to measure linear, nonlinear, mass or volumetric flow rate of a liquid or a gas.

Question { 5372 }

what is the simple meaning of harmonics?

Answer

A harmonic of a wave is a component frequency of the signal that is an integer multiple of the fundamental frequency, i.e. if the fundamental frequency is f, the harmonics have frequencies 2f, 3f, 4f, . . . etc. The harmonics have the property that they are all periodic at the fundamental frequency, therefore the sum of harmonics is also periodic at that frequency. Harmonic frequencies are equally spaced by the width of the fundamental frequency and can be found by repeatedly adding that frequency. For example, if the fundamental frequency is 25 Hz, the frequencies of the harmonics are: 50 Hz, 75 Hz, 100 Hz etc.

Question { 3154 }

what is vibration?

Answer

Vibration refers to mechanical oscillations about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire on a gravel road

Question { 3956 }

what role neutral plays in electrical circuit? If neutral is
not there what will be the effect

Answer

Since the neutral point of an electrical supply system is often connected to earth ground, ground and neutral are closely related. Under certain conditions, a conductor used to connect to a system neutral is also used for grounding (earthing) of equipment and structures. Current carried on a grounding conductor can result in objectionable or dangerous voltages appearing on equipment enclosures, so the installation of grounding conductors and neutral conductors is carefully defined in electrical regulations. Where a neutral conductor is used also to connect equipment enclosures to earth, care must be taken that the neutral conductor never rise to a high voltage with respect to local ground.
Neutral is a circuit conductor that carries current in normal operation, which is connected to ground (or earth).